1. Technical Field
The present invention relates to a technique for processing an image using image data and to a technique for printing an image.
2. Related Art
As a halftone process where image data with numerous gradations is printed using dot data with a smaller number of gradations, there are known an error diffusion method where density errors are distributed in pixels in the vicinity in a case of converting the number of gradations, an ordered dither method where dot data is generated using a dither mask where threshold arrangement is carried out with excellent dispersibility, and the like. In a case of using a dither mask where a blue noise characteristic is applied or using a Bayer dither mask, the dispersibility of dot arrangement is excellent and the reproducibility of an image is superior with data with comparatively few changes in gradation has a two dimensional spread. In addition, the ordered dither method has an advantage in that it is possible to control forming of dots by applying a specific characteristic to the arrangement of thresholds in the dither mask.
For example, in a method which is illustrated in Japanese Unexamined Patent Application Publication No. 2007-15359 described later, by independently creating a dither mask which is used in determining the forming of dots during forward movement and a dither mask which is used in determining the forming of dots during backward movement in a case where bidirectional printing is performed and applying a blue noise characteristic to each of the dither masks, printing is possible with little reduction in image quality with regard to deviation in positions for forming dots which are the printing positions in both dither masks.